It's actually quite a deep position (much better than a few years ago when it was absolutely horrible), but since Shaq declined we've yet to see truly dominant centers like Kareem or Wilt who seem almost bigger than the league itself.
Dwight is the only elite center and he's clearly not at that level, even at his best. Bynum and Cousins have elite capabilities, unfortunately they're also largely flawed in ways that elite centers from the past weren't.
Some Cs are elite complementary players, however: Gasol (who has a poor man's Bill Walton thing going on), Tyson Chandler...

The only thing I disagree with is Marc Gasol...I agree that he's a poor man's Bill Walton but that's true enough for him to be a legitimate all-star PLAYER. He'll never be top 10, but he's more than a complimentary player.